The present invention relates to flash devices using light emitting elements including light emitting diodes.
In the past, there are conventional cameras and digital cameras that pick up an image of an object, using a CCD- or MOS-type solid-state image pickup device and record the image data on a recording medium such as a flash memory. In such cameras, a built-in or external strobe is used in order to compensate for an insufficient quantity of exposure light, for example, in image pickup. Generally, the strobe uses a xenon bulb as a light emitting element. The xenon bulb emits light when in response to a trigger signal it is supplied with power stored beforehand in a main capacitor. The charging of the main capacitor is performed immediately after the power supply or the strobe is turned on. However, it takes several seconds until the main capacitor is completely charged. Therefore, the image pickup is impossible during such charging time in the strobe using the xenon bulb. In addition, even a small main capacitor has a diameter of about 10-mm and a length of about 25–40 mm, so that miniaturization of the flash device is difficult.
Under such situation, it has been proposed that a light emitting diode (LED) should be used as a light emitting element to eliminate a need for the main capacitor and that a different kind of LED should be used to emit different-colored rays of light from the strobe. Generally, the light emitting diodes emit rays of light having uneven brightnesses and are ranked according to brightness. In use, light emitting diodes in an acceptable rank are used selectively.